Exemplary embodiments pertain to the art of power generation and, in particular, regulating a direct current (DC) voltage generated by a permanent magnet generator.
A conventional DC power generating system utilizes a 3-phase variable-speed permanent magnet generator (PMG) and an active rectifier. PMG's offers high efficiency and high power density in comparison with a wound-field synchronous generator. However, the size of the conventional two-level six switch active rectifier requires large size passive components, such as dc link capacitor and output power quality filter.
To achieve a high power density, multilevel topologies, such as an unidirectional Vienna Rectifier or a bi-directional neutral diode clamped multilevel converter, have been considered to achieve low harmonic distortion with moderate switching frequency and reduced EMI emissions compared to a standard 2-level active rectifier/inverter. However, these topologies are complex and expensive.
An alternative is to utilize a flux regulated (FR) PMG. In a flux regulated PMG, a controller can be utilized to control a current provided to a coil in the FR PMG that can fine tune the voltage output. However, in such cases, FR PMG output voltage buck regulation is limited to only 10-30% of nominal voltage at the rated load.